Sephadex G 200 column determination of the molecular weight of matrone in Aedes aegypti mosquitoes will continue in order to confirm with precision the data obtained the first year. The new form of biological assay, substantially shorter than the one formerly employed, will be used in these experiments. Attempts will be made to develop an immunoassay for matrone and to trace immunologically sites of synthesis in the male and sites of action in the female.